Electric lamp with single ended pinch seal



Aug. 30, 1966 e. K. DANKO ELECTRIC LAMP WITHSINGLE ENDED PINCH SEAL Filed June 26, 1963 lnvervtov. George M. Danko b5 HIS A t to neg United States Patent 3,270,237 ELECTRIC LAMP WITH SINGLE ENDED PINCH SEAL George K. Danko, Chesterland, Ohio, assignor to General Electric Company, a corporation of New York Filed June 26, 1963, Ser. No. 290,755 2 Claims. (Cl. 313-220) The present application is a continuation-in-part of my application Serial No. 203,237, filed June 18, 1962, now Patent No. 3,194,625 and assigned to the same assignee as the present invention.

This invention relates generally to electric lamp structures and methods of manufacture, and more particularly to lamps embodying a single ended pinch seal construction wherein an end of the lamp envelope is closed by a compressed pinch seal through which extend the lead-in conductors.

It isan object of the invention to provide a pinch seal lamp structure and manufacture which is adaptable to automatic equipment. It is a further object to provide a pinch seal lamp structure utilizing an exhaust tube extending through the seal area but without leaving in the seal area a relatively large channel or chamber for condensation of a vaporizable substance forming part of the atmosphere in the interior of the lamp envelope.

The novel features of the invention will appear from the following detailed description taken in conjunction with the drawing wherein:

FIG. 1 is an elevation of a lamp tion; and

FIGS. 2 to 9 illustrate various steps in the assembly of the lamp.

Referring particularly to FIG. 1 of the drawing, the lamp illustrated herein is of the high intensity compact iodine-cycle type comprising a tubular bulb or envelope 1 containing a longitudinally extending filament 2 of coiled tungsten wire, here shown as a coiled coil, and a gas filling including a small quantity of iodine vapor and an inert gas such as nitrogen, argon, krypton or xenon or mixtures thereof at a pressure of preferably at least several hundred millimeters of mercury, and even substantially exceeding atmospheric. In accordance with the teachings of Patent 2,883,571 Fridrich and Wiley, the iodine serves as a regenerative getter to maintain the walls of the bulb 1 free from deposits of tungsten vaporized from the filament. In view of the requisite high operating temperature, wherein the 'walls of the bulb 1 attain a temperature in excess of 250 C., for example about 500 C., the bulb 1 is made of glass having a relatively high softening point, such as one of the well known so-called hard glasses like borosilicate or aluminosilicate glasses, or quartz glass. The filament 2 is of any desired capacity sufficient to maintain the required bulb wall temperature, for example about 150 watts or more for operation from conventional power supp-1y sources of about 110 or 220 volt-s.

The filament 2 is supported by long and short inner lead wires 3 and 4 respectively, which may be of tungsten wire and which extend into and are heremetically sealed in a compressed pinch seal portion 5 at the end of the hard glass bulb 1. The inner lead Wires 3 and 4 are connected to respective outer lead Wires 6 and 7 which have their upper ends embedded in the pinch seal 5 and which may be sufliciently rigid to support the lamp. The filament 3 may be additionally supported by a tungsten support wire 8 (see FIG. 7) having one end embedded in the upper end of an exhaust tube 9 and its other end formed into a loop encircling the filament 2 at a point intermediate its ends. Although in some cases the composite lead wires 3, 6 and 4, 7 may be made of a single continuous length of wire such as tungsten, as here illustrated the outer leads 6 and 7 are composed of heavier embodying the invenwires of different composition such .as a nickel-iron alloy known as 52 Alloy (52% nickel and the remainder substantially iron) or piano wire, for example.

The glass exhaust tube 9 extends through the interior of the pinch seal 5 forming a passage or cavity 10 therethrough and in communication with the interior of the bulb 1 during manufacture of the lamp. In accordance wit-h the invention and as explained more fully hereinafter, the passage 10' is sealed off by heating and collapsing and sealing the walls of said passage at a localized area 11 in the pinch seal 5 remote from the outer end of said pinch seal and closely contiguous to the interior of the bulb 1. By closing off the passage 10 at a location as close as possible to the interior of the bulb 1, virtually the full length of the passage or cavity 10 may be closed off from the interior of the bulb to thereby avoid the presence of a condensation chamber in which the iodine could condense and be eifectively removed from the interior of the bulb.

In the manufacture of the lamp, as shown in FIG. 2 the upper end of the exhaust tube 9 is preferably heated and upset to form a button 12, and one end of a straight length of the support wire 8 is inserted into the softened button 12. During this operation the exhaust tube 9 may be supported in a support member or spindle 13 as shown somewhat diagrammatically in FIG. 3, the said holder :13 being one of a number of such holders carried at the periphery of the indexing turret of a mount-making machine similar to those well known in the art. The exhaust tube is loaded into an axial passage 14 in the holder 13 with its bottom engaging a shoulder 15, the pas-sage being sealed off by an O-ring seal 16.

Straight lengths of the lead wires 3, 6 and 4, 7 are dropped into respective passages 17 and 18 in the holder 13 and come to rest on a shoulder 19. Then the upper ends of the lead wires 3 and 4 are formed to provide laterally bent portions 20 with hooks in the ends thereof into which are inserted the ends of the filament 2, after which the hooks are clamped to firmly grasp the filament.

In the next step the support wire 8 is bent to the shape shown in FIG. 5 with a loop in its free end encircling the filament 2 at its midpoint.

Then, as shown in FIG. 6, the glass envelope 1 is dropped over the assembly of filament 2 and lead wires 3, 6 and 4, 7 with its open lower end resting on a shoulder 21 (FIG. 3) on the support member 13. Then a flow of inert or reducing gas, for example nitrogen, is started into the lower end of the exhaust tube 9 by way of a passage .22 (FIG. 3) in the support member 13, in order to protect the filament and other wires inside envelope 1 from oxidation, after which a zone of the envelope 1 adjacent the upper end of the exhaust tube 9 is heated by flames from burners indicated at 23. The burners 23 are actually directed at the envelope 1 in directions at right angles to those shown in FIG. 6, that is, they are located at opposite sides of the plane containing the lead wires 3, 6 and 4, 7. The said zone is heated to its softening point and the walls of the envelope 1 are collapsed and then compressed by a pair of pinch jaws, not shown, to form the seal area 5 (FIGS. 7 and 8) in which are hermetically sealed and embedded portions of the lead wires 3 and 4. The said pinch jaws are relieved or notched at the center in known manner so that the inner walls of envelope 1 in area 5 are fused and hermetically sealed to the outer walls of the exhaust tube 9 without closing the passage through the interior of the exhaust tube.

If desired, the portions of lead wires 3 and 4 which are embedded in the seal 5 may be precoated or beaded with glass in known manner.

The assembly thus formed and shown in FIG. 7, is then removed from the holder 13 (FIG. 3) and transferred to exhaust and gas filling equipment in which it is preferably supported in an inverted position as shown in FIG. 9. The envelope 1 is then exhausted and filled with the desired gas filling, such as argon and a small quantity of iodine. During the steps of filling with gas and with iodine vapor, the lower end of the envelope 1 is preferably cooled with liquid nitrogen to condense the iodine vapor and to lower the pressure of the gas filling below atmospheric. Then the envelope 1 is sealed off as shown at 11 in FIG. 9, preferably by locally heating the walls of the seal area 5 with burners indicated at 24 and either permitting the glass to collapse or compressing with pinch jaws to form the seal 11.

The portion of exhaust tube 9 extending beyond the pinch seal 5 may then be removed in any convenient manner, for example by simply snapping or cracking it 0E to complete the lamp structure shown in FIG. 1.

The lamp may be mounted in a socket by using outer lead wires -6 and 7 of sufficient size to serve as termnial pins or prongs for insertion into the contacts of a socket. The lamp may also be mounted in an outer bulb and base assembly for use in conventional sockets as shown, for example, in application Serial No. 274,461, filed April 22, 19*63'by F. A. Mosby and assigned to the same assignee as the. present invention.

As pointed out above, by sealing or tipping off the lamp at 11 in the pinch seal area around the exhaust tube 9 at a location immediately contiguous to the interior of the envelope 1, instead of conventionally tipping oif the exhaust tube 9 at the'exterior of the seal 5, I effectively avoid the presence of a condensation chamber due to the presence of the passage 10' formed by the residue of exhaust tube 9 left within the seal 5. Thereby, condensation of the iodine in such a chamber is avoided.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric lamp comprising a glass envelope containing a light source and having its end closed by a flattened pinch seal, a pair of lead-in conductors extending longitudinally through said seal from said light source, and a residue of glass exhaust tubing sealed in and extending longitudinally through .said pinch seal and defining a passage to the interior of said envelope, the walls of said passage being collapsed and sealed at a localized area remote from the outer end of said pinch seal and closely contiguous to the interior of said envelope.

2. An electric lamp as set forth in claim 1 wherein the light source is a tungsten filament and the envelope contains a filling of inert gas and a quantity of iodine.

References Cited by the Examiner UNITED STATES PATENTS 2,159,794 4/ 193 8 Hagen 313-220 2,664,517 2/ 1952 Wiener 174-1705 2,749,203 6/ 195 6 Hardwick 31618 2,883,571 5/1959 Fridrich et al. 313179 2,914,371 11/ 1959' Wiede-nmann 3 l6-2O 2,999,180 2/19-61 Howles 313--318 3,091,718 5/1963 Shur-gan 313222 JAMES W. LAWRENCE, Primary Examiner. GEORGE/N. WESTBY, DAVID GALVIN, Examiners.

R. L. JUDD, Assistant Examiner. 

1. AN ELECTRIC LAMP COMPRISING A GLASS ENVELOPE CONTAINING A LIGHT SOURCE AND HAVING ITS END CLOSED BY A FLATTENED PINCH SEAL, A PAIR OF LEAD-IN CONDUCTORS EXTENDING LONGITUDINALLY THROUGH SAID SEAL FROM SAID LIGHT SOURCE, AND A RESIDUE OF GLASS EXHAUST TUBING SEALED IN AND EXTENDING LONGITUDINALLY THROUGH SAID PINCH SEAL AND DEFINING A PASSAGE TO THE INTERIOR OF SAID ENVELOPE, THE WALLS OF SAID PASSAGE BEING COLLAPSED AND SEALED AT A LOCALIZED AREA REMOTE FROM THE OUTER END OF SAID PINCH SEAL AND CLOSELY CONTIGUOUS TO THE INTERIOR OF SAID ENVELOPE. 